1. Field of the Invention
The present invention relates to an apparatus and method for washing a substrate, in which a substrate such as a semiconductor wafer or an LCD substrate is washed by scrubbing.
2. Discussion of the Background
In a process of manufacturing a semiconductor device such as an LSI, a surface of a wafer on which a circuit pattern is formed is required to maintain a strictly high cleanliness, making it necessary to wash the wafer surface frequently both before and after various process steps. Particularly, in a photolithography process, it is absolutely necessary to apply a washing treatment to a wafer surface.
A scrubber disclosed in, for example, Japanese Patent Disclosure (Kokai) No. 57-102024 or Japanese Patent Disclosure No. 62-259447 is used in the photolithography process for scrubbing the wafer surface for the washing purpose. In the scrubber disclosed in these prior art, a washing liquid is supplied onto a surface of a wafer revolved on its own axis. Also, a washing member such as a brush or sponge, which is kept rotated, is brought into contact with the revolving wafer surface so as to remove the foreign matter attached to the wafer surface.
FIGS. 1 and 2 collectively show a conventional front face washing section 101. As shown in the drawings, the front face washing section 101 comprises a holder 103 having a washing liquid supply hole 102 formed in a central portion, and 6 washing members 104 held by the holder 103. The washing section 101 is supported by a support mechanism (not shown) so as to be rotatable on its own axis and movable in a vertical direction. The washing member 104 consists of a columnar sponge having a tip portion cut to form a flat surface. A washing liquid such as pure water is supplied through the washing liquid supply hole 102 into each of the washing members 104 while the washing section 101 is kept revolved on its own axis. Under this condition, the tip portions of the washing members 104 are pressed against a front face, i.e., circuit pattern-forming face, of a wafer which is kept revolved on its own axis, so as to cleanse the wafer front face.
FIGS. 3 and 4 collectively show a conventional rear face washing section 111. As shown in the drawings, the washing section 111 comprises a holder 112 having a washing liquid supply hole 115 formed in a central portion and a plurality of washing members 113, 114. The washing section 111 is supported by a supporting mechanism (not shown) so as to be rotatable on its own axis and movable in a vertical direction. The washing members consist of 8 brushes 113 and 4 sponges 114. These brushes 113 and sponges 114 are used in combination in the conventional rear face washing section 111 partly because the rear face of the wafer tends to be stained more severely than the front face and partly because the rear face can be scrubbed more strongly than the front face. Each of these brushes 113 and sponges 114 has its tip portion cut to form a flat surface which is brought into contact with the wafer surface. A washing liquid such as pure water is supplied through the washing liquid supply hole 115 onto each of the washing members 113, 114, while revolving the washing section 111 on its own axis. Under this condition, the washing members 113, 114 are pressed against a rear face (back face opposite to the circuit pattern-forming face), of the wafer W which is kept revolved on its own axis so as to cleanse the rear face of the wafer W.
In the conventional scrubbers 101, 111 shown in FIGS. 1 to 4, only a slight inclination of the supporting arm (not shown) causes the tip portions (wafer-contact portions) of the sponges 104, 114 to fail to be brought into contact uniformly with the wafer faces. In other words, peripheral portions alone of the sponges 104, 114 are strongly pressed against the wafer faces. Since the contact pressure between the sponges 104, 114 and the wafer face is locally concentrated, the entire wafer face cannot be washed uniformly. In addition, stains are attached to and remain on the peripheral portions alone of the sponges 104, 114. It follows that, if these sponges 104, 114 are used repeatedly, a serious problem is brought about that the wafer faces are stained.
An object of the present invention is to provide an apparatus and method for washing a substrate, which is effective for preventing a mutual pressing force between a scrubbing member and a substrate surface from being locally concentrated and permits allowing a substrate-contact portion of the scrubbing member to be kept clean.
According to an aspect of the present invention, there is provided a substrate washing apparatus, comprising:
a spin chuck for holding and rotating a substrate;
a brushing section including a scrubbing member which is brought into contact with a washing surface of the substrate held on the spin chuck and revolved on its own axis together with rotation of the spin chuck;
a washing liquid supply mechanism for supplying a washing liquid through the brushing section onto the washing surface of the substrate;
a pressure control mechanism for controlling a pressing force of the scrubbing member against the washing surface of the substrate; and
a moving means for moving the scrubbing member relative to the substrate in a radial direction of the substrate,
wherein the scrubbing member includes:
an abutting section which is brought into contact with the washing surface of the substrate; and
a non-contact peripheral section positioned about the abutting section and formed not to contact the washing surface of the substrate when the abutting section is in contact with the washing surface of the substrate.
If the non-contact peripheral section of the scrubbing member is curved in three dimensional directions to form a hemispherical configuration, the pressure concentration can be suppressed. Therefore, even if an arm supporting, for example, a washing member is inclined, the contact pressure can be made uniform over the entire contact region between the washing member and the washing surface of the substrate.
It is desirable for the sponge portion of the scrubbing member to be formed of a foamed polyvinyl alcohol (PVA) or a foamed polyvinyl formal (PVF).
In the present invention, the supply pressure of the washing liquid is variable, making it possible to control the swelling degree of the washing member by varying the supply pressure and, thus, to control the contact pressure of the washing member against the substrate.
According to another aspect of the present invention, there is provided a method of washing a substrate, comprising the steps of (a) arranging in a waiting section a scrubbing member including an abutting section which is brought into contact with a washing surface of the substrate, and a non-contact peripheral section positioned about the abutting section and formed not to contact the washing surface of the substrate when the abutting section is in contact with the washing surface of the substrate, the waiting section being positioned outside of a spin chuck and provided with a cleaner member for removing stains from the scrubbing member to cleanse the scrubbing member, (b) mounting a substrate on the spin chuck, (c) rotating the substrate together with the spin chuck, (d) moving the scrubbing member from the waiting section to an operating section near the substrate to permit the abutting section of the scrubbing member to be brought into contact with a washing surface of the rotating substrate, and supplying a washing liquid through the scrubbing member. onto the washing surface of the substrate, (e) moving the scrubbing member relative to the substrate in a radial direction of the substrate while the abutting section of the scrubbing member is in contact with the washing surface of the substrate so as to have the washing surface of the substrate scrubbed with the abutting section, and (f) bringing the scrubbing member after the scrubbing operation back into the waiting section and rotating the scrubbing member about its own axis in contact with the cleaner member of the waiting section, the washing liquid being spurted outward from inside the scrubbing member during revolution of the scrubbing member in the waiting section so as to remove stains from the scrubbing member.
In the washing method of the present invention, the washing member itself is washed while the washing member is positioned in the waiting section. Also, the dust or the like attached to the surface of the washing member is removed by a washing liquid spurted from within the washing member to flow to the outside through the washing member. Further, vibration is imparted to the washing liquid, making it possible to wash effectively the washing member itself.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.